Latest Publications

Watering the garden in April – how unusual is this?

Gardeners among the readership of this blog may already be watering their seeds in an attempt to ensure germination and early growth, and may be wondering how common this activity is (over the years) given the fact that spring is only halfway sprung and the past winter was not that dry overall.

One observation carried out each morning in the Reading University Atmosphere Observatory is that of determining the ‘state of the ground’, the observations being represented by one of 20 integer codes.  Some of these observations are made using a weeded, plot of bare soil in the Observatory enclosure.

Thus, as well as determining whether the ground is snow-covered, the duty observer will, in the absence of any snow or ice cover, decide whether the bare soil patch can be described a dry, moist, wet, flooded or cracked, for example. The World Meteorological Organization specifies 10 code figures for such descriptions – see Table 1. A similar table of codes exist to describe conditions when there is ice or snow on the ground – the observer uses one, but not both codes – on any given day.

Table 1. Codes use to specify the state of the ground when no ice or snow is lying (WMO code 0901 on page A-274 of These codes have been in use at the University since January 1982.

Code Description
0 Surface of ground dry (without cracks and no appreciable amount of dust or loose sand)
1 Surface of ground moist
2 Surface of ground wet (standing water in small or large pools on surface)
3 Flooded
4 Surface of ground frozen
5 Glaze on ground
6 Loose dry dust or sand not covering ground completely
7 Thin cover of loose dry dust or sand covering ground completely
8 Moderate or thick cover of loose dry dust or sand covering ground completely
9 Extremely dry with cracks

Recently (as of 20 April 2015) the Reading observations indicate 8 consecutive mornings with the ground being ‘extremely dry with cracks’ (there had also been 2 similar observations earlier in the month. No doubt this total has been helped by a fall of just 6.3 mm of rain so far in April 2015 – well below the average of 48 mm expected for the month.

Of course, soils vary and the response of a particular soil to the effects of wind/rain/sunshine/air humidity and temperature will depend upon the mineral and organic matter composition of the soil (gardeners will be well-aware of the benefits of an organic mulch, for example, and of the way that clay-rich soils tend to be heavy and retain moisture).

Clay soils are also more prone to cracking than are soils with a fine tilth. The clay particles act just like a sponge – they swell as they soak up water, and then they shrink as they dry out. In a spell of dry weather, the shrinkage can result in large cracks. In severe cases, these soils can undermine the foundations of buildings because they swell and shrink so much. Such conditions were widely reported during the dry spell of 1975-1976 in parts of the UK. In Reading during April-July 1976 (a different set of codes was in use then) 106 of the 122 days were reported as having ‘dry’ soil and only 16 were classified as ‘moist’. During 1982-2010 the number of days with moist soil was almost exactly the same as the count of dry or cracked soils during these four months on average – largely thanks to April 2007 (see Figure 1 below) when less than 1 mm of rain fell all month.

So how do the ’10 soil cracked days’ of 2015 compare with measurements made in April over the years? The answers are in Table 2.

Table 2. Averages of daily count of measurements of the state of the bare soil patch (1982-2010) when snow/ice-free, and the maximum count of given conditions in a single calendar month (1982-2014). These are compared to the observations of 1-20 April 2015.

Code Average occurrence in April, 1982-2010 Greatest number of occurrences in April, 1982-2014 1-20 April 2015 total
0 8.0 21 3
1 19.5 30 6
2 0.2 3 1
3 0 0 0
4 0 1 0
5, 6, 7, 8 0 0 0
9 2.1 14 10
Mornings with snow/ice cover 0.2 2 0

Table 2 shows that a cracked ground is reported in April on about two days each April on average. In fact, April tends to account for about half the annual count of cracked soils in Reading on average during 1981-2010.

Figure 1. Year-by-year count of number of days with cracked ground in April at the University of Reading, 1982-2014.

As with many on/off types of meteorological observations, the complete observational database indicates quite a variation in this count, however (Figure 1). Just 7 out of the 33 years had soil this dry, with only 5 of those having cracked soil on 5 mornings or more. Maybe there is a suggestion of an increased frequency of such events since 2002 – gardeners beware!

Spilling the beans on climate change

By Hannah Parker

Geography students studying ‘Resilience for Sustainable Development’ had a change from their normal lecture format recently, and instead played a game. This wasn’t just for fun though, as ‘serious gaming’ is becoming a popular way of sharing complex information with a range of potential users and giving them opportunity to discuss its use. The students played CAULDRON, a game developed by members of the ACE-Africa project (University of Reading (Parker, Cornforth and Boyd) and Oxford University) together with the Red Cross/ Red Crescent Climate Centre, who have lots of experience designing games to communicate climate information. This game was developed to present the science of extreme weather event attribution in an accessible way, and provide space for discussion about whether it could be used in climate policy.

CAULDRON stands for Climate Attribution Under Loss and Damage: Risking, Observing, Negotiating. This reflects the fact that loss and damage due to extreme weather events is occurring all over the world and people are taking an interest in whether this is due to climate change. Negotiations are also currently taking place to work out how to address this loss and damage under the United Nations Framework Convention on Climate Change (UNFCCC). The game gives players the chance to experience having to make decisions under uncertain climate risk, something many people have to do in reality every day. They also have to analyse changes in risk with only limited data and deal with the difficulties of negotiating with other players with different interests.

The game began with players given the role of farmers who had to plant crops each season. They were each given beans to symbolise their crops and a ‘rainmaker’, which was a small pot containing a dice, to shake to determine their rainfall each season. Players who had good rains gained more beans, while those with drought years lost beans. Some players ended up in crisis with too few beans to be able to plant, so had to try and strike up deals with fellow players to be lent beans so they could keep playing!

Climate change can affect the probabilities of extreme weather events occurring, so for the next part of the game players were given new rainmakers. Some of these contained dice with increased probability of drought which would ruin crops, but players didn’t know which … Suddenly, there seemed to be more droughts happening and more players getting into crisis.

Players try to figure out their best farming strategy

For the next part of the game, players became scientists. Using new rainmakers as ‘climate models’, they produced more statistics to help them work out whether their risk of drought had been altered by climate change. How trustworthy were the results provided by their models though?

Players became negotiators at the UN climate negotiations for the final part of the game. They had to work out how they were going to deal with the fact that some players had collected more beans than others. Some players had been acting as developed countries and so, along with fewer losses, they had greater historical emissions. Were they to blame for losses in the developing countries? After much debate, each group managed to come up with an agreement that all players were happy to sign. However, some players did say they felt they had been bullied into making agreements and noted that the developing countries were denying that climate change had happened at all! Solutions presented to address the loss and damage at the end of the game included clearance of debts that had accumulated between players, rules on farming strategies that would be used in the future, and agreements on transfer of beans for when players got into crisis. With such a range of ideas diplomatically expressed, maybe we have uncovered some of the negotiators of the future …

A spokesperson reads out his region’s signed agreement to address loss and damage

By the end of the game, all the players said their knowledge of extreme event attribution had been improved. One player said their understanding had been improved ‘by creating a situation where extreme events had “real” consequences and a political “reality” ‘. This is the key feature of participatory gaming, that players can experience the emotions involved and have to act under uncertainty rather than just learning about it theoretically. Furthermore, it provides insights into the challenges of climate negotiations and the inequality between developing and developed countries, along with the difficulties in separating the impacts of climate change from other factors.

This has been just one of the many times the CAULDRON game has been played, which have included players from sectors ranging from climate science to civil society. Each time the game has prompted lively discussion about event attribution science and dealing with the impacts of climate change and demonstrated that ‘serious gaming’ can be an effective, but also fun, way of sharing climate research.

A career in environmental science research … ?

The SCENARIO NERC Doctoral Training Partnership (DTP) at the Universities of Reading and Surrey is advertising 12-16 fully funded PhD studentships starting in September 2015.  SCENARIO seeks to attract high-quality graduates from science, mathematics and engineering degrees.  For a full list of available PhD projects and details on how to apply, please visit our website: .

The scope of SCENARIO is broad, spanning the science of the atmosphere, oceans, ice, hydrology, soil, biosphere and space weather. As a SCENARIO DTP student you can expect to receive excellent training in quantitative environmental science, research skills and a wider set of professional skills in preparation for a leading role in science, industry, the public sector or academia. SCENARIO has many partners from industry and the public sector who offer co-supervision and opportunities for placement work related to your PhD research. Look for details of CASE sponsorship in the project adverts.

NERC funding is only available to UK citizens and other EU citizens meeting the RCUK residence requirements. The studentships cover fees, training, research expenses, conference attendance and a tax free maintenance grant.

The deadline for applications is approaching soon – it’s 2 February 2015.

For further queries please contact Jill Hazleton, (SCENARIO DTP Administrator)

Solar Stormwatch

By Luke Barnard

Coronal mass ejections (CMEs) are eruptions of coronal plasma and magnetic flux from the Sun’s corona, out into interplanetary space. CMEs are widely recognised as being a main driver of space weather and those CMEs that travel on a trajectory that intersects Earth’s orbit can be highly “geo-effective”, potentially generating geomagnetic storms and affecting Earth’s radiation belts. The risks associated with CME-driven space weather hazards can, to some extent, be mitigated by accurately forecasting the time at which a CME will interact with the Earth system – more specifically, what time it will “hit” Earth’s magnetic field. Therefore, a major theme in space weather research is developing a better understanding of the physics of CMEs, especially the dynamics of CME propagation from the Sun to Earth.

We use the Heliospheric Imager (HI) instruments aboard the twin STEREO satellites to study the dynamics of CMEs. These are white-light cameras with a wide field-of-view that can image plasma motions such as CMEs all the way from the outer edge of the Sun’s corona to near-Earth space. The two STEREO satellites, each carrying a HI instrument, are in Earth like orbits, but one drifts ahead of Earth (STEREO-A) and one drifts behind (STEREO-B), separating from Earth by about 20 degrees per year. Therefore, HI images allow us to study CMEs travelling towards Earth from two different vantage points.


Figure 1: (A) An example of an image taken by the HI instrument aboard STEREO-A. Each HI consists of two separate cameras, HI1 with a 20 degree field-of-view (on the right), and HI2 with a 70 degree field-of-view (on the left). The cameras are aligned so that the ecliptic plane runs horizontally along the center; the Sun is located just outside the rightmost edge of the HI1 image, whilst Earth is located just off the leftmost edge of the HI2 image. (B) An image from HI1 that has been processed to remove the background stars and enhance the visibility of a CME, which can be observed on the right hand side as the higher contrast white and black regions.

However, there are challenges in using the HI data to study CMEs. Firstly, there is no absolute definition of what constitutes a CME and so their identification and characterisation is subjective. Secondly, the CME characterisation is typically done by manually analysing images, which is very time consuming. Finally, CMEs are sufficiently complex and variable that it is difficult to automate this analysis, which would reduce the subjectiveness and labour of our research.

Solar Stormwatch ( is a citizen science project that solves many of these problems. The project consists of several activities, completed via a web interface, where anyone who is interested can identify and characterise CMEs visible in the HI images.


Figure 2: An example of the Solar Stormwatch web interface in which CMEs are identified in the HI1 cameras aboard STEREO-A and STEREO-B.

For example, in one activity participants are asked to view a movie of HI images and to record the time at which they can see a CME enter the HI field-of-view from either STEREO satellite. When many participants tell us they can see a CME entering the HI field-of-view, we can be confident they are probably correct. In a second task, we direct participants to images in which the profile of a CME should be visible, and ask them to locate the front of the CME in the image. When many participants characterise the same CME, we can average their individual estimates to produce a consensus profile of the CME. This consensus profile does not suffer from the subjectiveness of an individual expert’s identification, and the variability of this average gives us new quantitative information about how well defined the event is. You can see the results of this process in the animation in Figure 3, which shows the propagation of a CME through the HI1 field-of-view, upon which the CME front identified by the Solar Stormwatchers has been overlaid in red. The yellow lines mark the outer-limits of the HI1 field-of-view analysed by Solar Stormwatch.

Figure 3 (link to animated GIF): This movie shows a sequence of HI1 images, processed similarly to Figure 1B, in which a CME can be seen to enter and propagate across the HI1 field-of-view. The yellow lines mark the outer limits of the image region analysed. The red lines mark the location of the consensus profile of the CME front, calculated by averaging the observations of many Solar Stormwatchers.

Solar Stormwatch has now been running for approximately 4 years, with input from more than 16,000 citizen scientists, resulting in a data set in excess of 38,000 characterisations of CME trajectories. We have recently turned these observations into a catalogue of CMEs observed by the HI instruments. This is a new and unique catalogue, providing information about CMEs at distances away from the Sun not presently covered by other widely used CME catalogues. These data are all publicly available, and we hope they will aid new research into the dynamics of CMEs – some of which is already being done here in Reading. The next stage of Solar Stormwatch is to update it with new data, as presently only the HI images from 2007 to 2010 have been analysed – with 2010 to 2014 left to analyse there is much more data to process!

To read more:

To take part:

ACKNOWLEDGEMENTS Many thanks to Chris Scott for Figure 1A.

Environmental Physics 2014 video competition results

By Matt Owens

Yesterday (Wednesday 26 November) was the screening event for the Environmental Physics 2014 video competition, in which we asked GCSE and A-level students to put together a one minute video describing an aspect of the physics of light.  The topic was chosen in support of UNESCO’s upcoming international year of light event.

The judges with second place winner, William Tyrrell

The entries covered a huge spectrum of topics [groan – Ed], as showcased below, from students all over the UK. The judging panel comprised a space physicist, a stratospheric physicist and a scientific outreach expert (with a murky past in astrophysics).  Using the new video wall facility, the panel and audience considered five shortlisted videos. After much deliberation (and cake), the following winners were announced:

First place:

Embla Hocking (Exeter Mathematics School) for her video, “Why can we see pink?”

Prize: iPad Mini and a cloud chamber for detecting cosmic rays to her physics department

Second place:

William Tyrrell (King’s College, Wimbledon) for his video, “Light speed

Prize: £100 of Amazon vouchers

Third place:

Philippa Copeland (Havant Sixth Form College, Southampton) for her video, “Lenses

Prize: £50 of Amazon vouchers


Mo Awe (Putney High School) and Alex Bytheway (Rydal Penrhos, North Wales) for their entries on “Gamma Rays” and “Photosynthesis,” respectively.

Prize: £20 of Amazon vouchers.

A big thank-you to everyone who took part and we hope for an equally successful competition in 2015!

Matt Owens

The end of the rainbow … an open letter to the climate science community

An open letter to the climate science community

By Ed Hawkins, Doug McNeall, David Stephenson, Jonny Williams & Dave Carlson

Dear colleagues,

This is a heartfelt plea.

A plea to you all to help rid climate science of colour scales that can distort, mislead and confuse. Colour scales that are often illegible to those who are colour blind.

The main culprit is, of course, the ‘rainbow’:

We have all likely used it, and we have all certainly seen it – presentations, posters, papers, blogs and news articles full of figures with similar colour scales.

However, the most commonly used rainbow colour scales can distort perceptions of data and alter meaning by creating false boundaries between values. There are numerous blogsand published papers from visualisation experts illustrating these issues. In one example, changing to a non-rainbow scale even improved accuracy of heart disease diagnoses.

And, if you use a rainbow colour scale, you will have a friend or colleague that is colour blind and may confuse the colours.

This is not the first such plea.

A decade ago an article appeared in EOS, demonstrating that contrasting red with green can render a figure illegible to the 8% of the male and 0.4% of the female population who are colour blind. The EOS article suggested that journals should do more to improve the colour accessibility of figures.

But, the problem is now worse than a decade ago. Most issues of every major climate journal have figures which are potentially misleading and colour inaccessible. Maps, line graphs and histograms can all have confusing colour combinations.

Journals, rightly, do not tolerate poor grammar, incorrect spelling, or muddy descriptions of scientific methods. It should be no different for visual communication. We should be equally intolerant to poor use of the grammar of graphics as we are to its written equivalent.

It is not just the journals who need to act. As scientists increase their efforts to make their work accessible to the public through the media, blogs and social media, there are more opportunities to show poor figures.

What are the possible solutions?

We need to be more willing to discuss and criticise the visualisation of the science as well as the science itself.

Authors should be responsible about the colour choices they make. Journals might add colour accessibility to their existing guidelines for acceptable figure types. Reviewerscould recommend revision if such colour scales are used. Editors should not accept papers which use inaccessible and potentially misleading colour scales. And, the mediamight reconsider using such figures from published work.

We know ‘rainbow’ is the default colour scale in many commonly used programming languages, but that doesn’t make it the best. Resources are easily available to change colour scales for RIDL (& here), MATLABPython.

There are numerous websites and online tools giving advice and recommending safe and better colour scales (such as Color Brewer or HCL Wizard). You can even test online how your figures might appear to those who are colour blind. Adding different shape markers in line graphs might also aid interpretation.

Choosing a good colour scale is not difficult – it just takes awareness and a few moments of effort. The best choice will probably depend on the situation, so ask yourself why you have chosen that particular colour scale.

We take heart from some recent progress.

The journal BAMS recently took a step forward by publishing an article pointing out the flaws with rainbow colour scales. MATLAB have just announced that they are changing the default rainbow colour scale, giving a comprehensive explanation considering colour accessibility and perception issues.

All of us could do more in improving the clarity of our figures, the authors of this open letter included. More needs to be done. And, it needs all of us to do more.

So, we undertake this pledge – to never again be an author on a paper which uses a rainbow colour scale.

If you agree to also make this pledge (or disagree), please comment below this post. Oremail us. And tell your colleagues.

We hope that you will join us.

We encourage the climate science community to communicate this letter widely. To spread the word on twitter, please use #endrainbow. Short URL:

Other climate-related case studies:

Example of simulating colour blindness with different colour scales & MATLAB software:Which colour scale is best for you?

Considering different colour scales for sea-level change maps: Better palettes

And, it is not just climate. One of the iconic images in astronomy – the Cosmic Microwave Background (CMB) – is normally in rainbow

Many thanks to all those who have patiently commented on these issues.

Space weather – sunspot AR2192

By Simon Thomas

Friday 24 October 2014 – updated 30 October 2014

Sunspots are areas on the Sun which appear dark in contrast to the solar disk. They are associated with complex magnetic fields which inhibit convection and are therefore not as hot as the surroundings (sunspots are typically 3000-4500 K compared to the surrounding at, on average, 5780K). The magnetic fields in sunspots are arranged vertically and are either pointing inwards or outwards. Therefore, when we discuss “sunspots” we are typically referring to sunspot-pairs, where the magnetic field points out of one, then loops and connects inwards to other sunspot.

Active regions on the Sun, including sunspots, are of interest to us as they are effectively source regions for solar flares and coronal mass ejections (CMEs). Solar flares are bright flashes interpreted as a huge release of energy. The emitted x-ray and ultraviolet (UV) radiation from solar flares can affect satellite communication systems at Earth. A flare is often, but not always followed by a CME, a subsequent eruption of plasma and magnetic field out from the Sun and into space. If a large CME erupts and impacts Earth, then it can trigger “geomagnetic storms” which can result in low-latitude aurora, disruption to power grids and enhanced radiation doses to humans at high altitude. Full space weather hazards and risks are discussed by Hapgood (2010).

The large sunspot AR2192, which has made the news this week, was not too unusual when it was last visible before rotating around the opposite side of the Earth. As our only spacecraft which view the Sun on the other side of the Sun are now turned off while the Sun is between them and Earth, we have not been able to follow the sunspot through its progression until recently. However, since it has rotated around and become visible to ground-based and observations from the Solar Dynamics Observatory, we have been able to observe and analyse its progression and development. See this link for a video clip of the progression of this sunspot from youtube.

So, why has sunspot AR2192 caused excitement within the media? Well, firstly it has just been confirmed to be the largest to be observed in almost 25 years. It is by far the largest sunspot in this current Solar Cycle and has been visible to the naked eye (with the help of filters – don’t look directly at the Sun!). This interest has been enhanced as it coincided with a recent partial eclipse viewable from the USA. To be able to comprehend the size of such a sunspot, as the pictures on the solar disk do not give it justice, we can compare with the sizes of the planets. This is shown in Figure 1 where the sunspot on the 22 October is shown to scale to be approximately the size of Jupiter, and 14 times the size of Earth.

Figure 1 – Sunspot AR2192 on 22 October 2014 compared to the sizes of Jupiter and Earth. Image courtesy of

Since this image was taken, the sunspot has grown larger still.

The second point relating to our interest in this sunspot is in the history of such sizeable sunspots. The last time we saw a sunspot of comparable size, it was associated with consecutive Earth-directed CMEs known as the “Halloween Storms” which took place in 2003. These caused aurora to be observed as far south as Texas and the Mediterranean, and caused a power outage in Sweden.  There have, however, been larger sunspots since records began. Figure 2 shows a graph of the largest yearly sunspots of the 20th Century. The largest peak on here is the so called “Great Spot of 1947”. This grandly-named sunspot was the largest recorded, but in contrast to the 2003 event that produced the Halloween Storms, this, it appears, did not produce a large Earth-directed CME. This does not, however, mean that it did not release a huge CME in a different direction as it rotated around, but it is unfortunate that we have only had a means of observing remote coronal mass ejections and flares in recent years.

It is worth discussing now that just because a sunspot is large, this does not necessarily mean it is capable of producing hazards to us on Earth. Firstly, the active region (including the sunspot) must have suitably complex and compressed magnetic fields to release a CME in the first place. Secondly, even if the active region is capable of producing CMEs, the eruption of this CME would have to be at the correct angle to intercept Earth. CMEs in the solar system are fairly large structures, but Earth is a small target compared to the number of possible trajectory angles of the CME.

Figure 2 – Largest yearly sunspots observed from 1900-2000 in millionths of the total solar disk. Courtesy of David Hathaway, NASA.

So, with that said, what are the prospects of getting some significant space weather from AR2192? Currently, the new Met Office space weather prediction centre have been keeping a close eye on the evolution of this sunspot and this is a sizeable, early challenge for their forecasters. The sunspot group has been producing a high frequency of powerful solar flares, but as of yet, no significant CMEs in our direction. This led the Met Office to release the following forecast on 23 October 2014, for the weekend: “Solar activity is likely to remain at moderate to high levels with a chance (30%) of X-class flares. Geomagnetic activity is expected to remain elevated as a further coronal hole high speed stream becomes geo-effective but with only a slight chance (15%) of minor storms”. The coronal hole part relates to a large, slightly darker region of the Sun ahead of AR2192 which has been releasing faster solar wind than the ambient wind speed.

The predictions from the Met Office and a similar forecast from NOAA show that it is very likely that there will be further solar flares, perhaps up to the most intense, X-class of flare. However, it does appear that there is a low chance of a CME impacting in the next ~3 days. However, this does not mean that this would not happen in the slightly longer term; CMEs generally take a matter of days to reach Earth and so as the sunspot is now Earth-directed, a CME associated with an anticipated flare may not reach us until early next week. Such a flare with an associated CME has not occurred, as of 1500 UTC on Friday 24 October.

Finally, let’s think about the longer term. Are we likely to see any more sunspots of this size in the coming years and what is the chance of a large Earth-directed CME? The sunspot cycle has just peaked at solar maximum and solar activity is starting to decline. As the maximum sunspot size roughly follows the sunspot cycle, it is unlikely that we shall see another of this size for a good few years, but not impossible! Secondly, solar activity in general appears to be in decline from the very large cycles we saw in the late 20th Century. The latest solar cycle has been very weak compared to previous cycles in both sunspot numbers as well as solar wind parameters such as the magnetic field in near-Earth space. This is shown in the top two panels of Figure 3 (from Lockwood et al., 2012). These show the sunspot number (R) in the top panel and the near-Earth magnetic field in the second. The black lines in these are the data and it is apparent that the number of sunspots has began to decline here and this has coincided in the magnetic field drop.

Figure 3 – Data and predictions from Lockwood et al. (2012) of sunspot number (R; top panel), the near-Earth magnetic field strength (B; second panel), cosmic ray number from a station in Finland (Onm; third panel), and the aa index, showing changes in the Earths magnetic field (aa; final panel). Black lines are raw data, purple lines are reconstructions and red to blue are likely patterns that the observations will follow.

With the number of sunspots reducing, it is unlikely that there will be as frequent “super-sunspots” as were seen during the last century. Moreover, the predictions from Figure 3 (based on predicted variations from previous scenarios in ice-core data) show that sunspot number is likely to reduce even further with weaker magnetic fields. Thus, although solar activity is very difficult to predict, sunspot AR2192 has given us a rare opportunity to study the evolution and activity of such a sizeable sunspot, which will hopefully give a useful and significant contribution to future space weather forecasts.

UPDATE (30 October): As AR2192 is disappearing around the east (right-hand) limb of the Sun, it is still increasing with size. It has produced a large number of M- and X- class solar flares but no sizeable coronal mass ejections, which was as anticipated by the Met Office prediction centre. Sunspots can persist for several solar rotations (which take approximately 27-days to complete), and so it is possible that we shall see the active region again in a few weeks.


Hapgood, M.A., 2010. Towards a Scientific Understanding of the Risk from Extreme Space Weather. Adv. Space Res., 47, 2059–2072

Lockwood, M., M. J. Owens, L. Barnard, C. J. Davis, and S. R. Thomas, 2012. What is the Sun up to? Astron. and Geophys., 53, 3.9–3.15

An analogue forecast for winter 2014/15 in Reading

By Roger Brugge

Reluctant as I am to do long-range predictions, analysis of Reading data for the period 1961-2010 suggests the following:

Rainfall – 2014 has given us a dry September and (already) a wet October. Let’s assume that overall autumn rainfall is close to normal. After an autumn with normal rainfall the likelihood of winter being

  • Wet/very wet  is 17%
  • Normal: 50%
  • Dry or very dry: 33%

October has been a dull month so far after near-normal September sunshine. Overall the autumn may well have close to normal sunshine. After a ‘normal’ autumn we find that winter sunshine was as follows:

  • Sunny or very sunny is 23%
  • Normal : 57%
  • Dull or very dull: 20%

Finally, autumn has so far been a warm season with a mild October after a warm September. Warm or very warm autumns are followed by winters that were

  • Mild or very mild is 56%
  • Normal: 12%
  • Cold or very cold: 32%

So, a tongue-in-cheek forecast at this mid-way point in October would be for a winter in Reading that is close to normal in terms of rainfall and sunshine, but probably milder than average.

17 October 2014

Tornadoes in the UK?

By Tom Frame

Last Wednesday (8 October) saw reports of several tornadoes in the UK – one even tore the roof off a house. I remember whengrowing up I always thought of tornadoes as something that occurred only in the USA – perhaps a school production of The Wizard of Oz had put this in my mind. So a few years ago (probably more than a few now), the first time I ever heard of tornadoes in the UK, I was pretty shocked. But just how common are these?

When I asked around I was told that it is often said that the UK has the highest number of tornadoes per year per square kilometre in the world. Is this really true? Interestingly a study published in 2003 (reference 1) seems to suggest that the UK has a fairly high number – but the highest? No …
It turns out that if you go by actual number of tornadoes observed , then the Netherlands has the most, Estonia second, Republic of Ireland third, the UK fourth and the USA fifth. Whereas if you go by an estimate of the true number then the UK jumps up to second place behind the Netherlands.
So tornadoes in the UK – not a big surprise.
The real reason that the USA is strongly associated with tornadoes is that it has the most intense and damaging tornadoes in the world. So whilst the UK has many, they are weak and short-lived usually causing only minor damage.
Reference 1
Dotzek, Nikolai. “An updated estimate of tornado occurrence in Europe.” Atmospheric Research 67 (2003): 153-161.

The ozone layer shows first signs of recovery, but …

By Michaela I. Hegglin

Just over two weeks ago, the United Nations (UN) held a press conference in New York to announce the release of the Assessment for Decision Makers (ADM), a summary document of the WMO/UNEP Scientific Assessment of Ozone Depletion 2014. The report is the work of a UN panel of 300 scientists from around the world (including four scientists from our Meteorology department) and represents the latest comprehensive update on the state of the Earth’s ozone layer, which protects the Earth from the Sun’s harmful ultraviolet radiation.

Figure 1: The ozone layer is on its way to recovery. The past evolution of ozone observations is well understood and can be modeled by complex chemistry-climate models (CCMVal-2 simulations in black with uncertainty in grey). Pink curve shows the potential of ozone-depleting substances to destroy ozone in the stratosphere (EESC; pink). Other colors show ozone evolution for different representative pathway scenarios (RCPs). (Source: ADM, WMO/UNEP ozone assessment, 2014).

The encouraging finding of this year’s Assessment is that the ozone layer is showing first signs of recovery. A reduction in ozone depletion is expected given the decline in stratospheric chlorine abundances by 10-15% since peak values in the late 1990s/early 2000s. However, the detection of ozone recovery has been anything but trivial, since the signal has to be disentangled from natural variability, enhanced ozone depletion after the Mt Pinatubo volcanic eruption in 1991, increases in tropospheric ozone, and the impact of climate change, all of which affect total column ozone in addition to ozone-depleting substances. While the observed increase in total column ozone seen in Figure 1 is consistent with model predictions, the authors of the Assessment were not ready to attribute it with high confidence to the decline in ozone-depleting substances (although a subsequent study by University of Reading authors has now done so*). Therefore the Assessment states that there are ‘indications of recovery’ and not yet recovery itself.

Astonishingly, there are skeptics who deny ozone depletion has ever happened. Reactions such as ‘Oh, so the ozone hole was just yet another scare-story of the environmentalists, such as acid rain and climate change?!’ were to be heard days after the ADM-release. Well, we definitely know better. If the world would not have reacted quickly to the threat from ozone-depleting substances, we would be in serious trouble now. At the time of the Montreal Protocol, ozone-depleting substances were set to grow at a rate that by today would have caused at least twice the ozone depletion that we have experienced (see Figure 2). Stopping and reversing the growth of the atmospheric concentrations of ozone-depleting substances has thereby helped avert an estimated 2 million skin cancer cases per year by the year 2030.

Figure 2: The world avoided. Without the Montreal Protocol, the global ozone layer would have experienced serious depletion around the globe. The change from red in 1989 to green-yellowish colours in 2028 indicate a thinning of the ozone layer by around 20%  (credit: Paul Newman, NASA Goddard, USA)

The bad news… Although the Montreal Protocol has averted the worst outcome of ozone depletion, the ozone layer is never expected to return to a pristine state. The culprit is climate change as discussed in the ADM.  Models predict that the ozone layer will be strongly affected by greenhouse gases due to both physical and chemical mechanisms. Nitrous oxide (N2O) and methane (CH4) both affect ozone chemically. Carbon dioxide (CO2) cools the stratosphere and also leads to increases in stratospheric ozone due to a slowing down of chemical loss reaction rates, ironically ‘helping’ the ozone layer to heal. Finally, the combined greenhouse effect of these gases increases the strength of the stratospheric overturning circulation. The strengthened circulation leads to a decrease in total column ozone in the tropics, and to an increase in the extratropics, the extent of which is dependent on the greenhouse-gas scenario the world will follow into the future (see Figure 1). However, too little UV radiation (as a consequence of a thicker ozone layer) can have adverse health impacts too, especially at higher latitudes where it is well known to lead to Vitamin-D deficiency and ailments such as rickets.  But because the ozone decrease expected from climate change will be in the tropics, it may this time affect people who are least educated about the ozone layer, and who have the least means to protect themselves.

The work is not done yet, moreover, since the substitute gases currently used by industry to replace the ozone-depleting substances are themselves strong greenhouse gases and if left unabated may contribute 10% or more to the climate forcing from CO2 by the year 2050. The problem is identified and industry seems to be at least prepared to investigate solutions. The latter was a key aspect throughout the process of the Montreal Protocol: bringing all stakeholders to the table — scientists, industrialists, economists, legal experts and policymakers — to find a compromise on how to deal with this global environmental issue. It took almost 30 years before the policy action has borne fruit. But full recovery of the global ozone layer is not expected before the middle of the century, and even later in the Antarctic –  a reminder of how long environment damage can accompany us. Even more so, the Montreal Protocol should give us hope that humankind is able to tackle climate change, and its mechanisms may well serve as an example of how to do it (see also commentary in the Guardian